1. Field of the Invention
The present invention relates to computer input devices. More particularly, the present invention relates to computer input devices which are suitable for making drawings with a pen, stylus, or finger.
2. The Prior Art
In a computer system having software for drawing, painting, or otherwise entering picture information, a user of the computer system will often desire to use an input device to draw pictures, write, or execute a signature, etc. In such cases it would be advantageous if the input device could emulate the drawing or writing behavior of a physical device with which the user is familiar, such as a physical pen with ink. When the input device acts in an unfamiliar manner, drawings created by the user may be sloppy or ill-formed and may thus result in user dissatisfaction.
One aspect of the behavior of a physical pen is that it applies ink in a written stroke, immediately visible to the user, when a writing point of the physical pen is applied to paper. At any time, the user is able to pick up the physical pen and place it elsewhere on the paper, so as to begin a new written stroke, and the user is able to determine the new location of the pen in response to written strokes which have already been drawn on the paper. One problem which has arisen in the art is that the computer system and the input device do not provide a convenient method for allowing the user to xe2x80x9cpick up the penxe2x80x9d and continue to draw in a new position accurately selected by the user in response to written strokes which have already been drawn.
One known method for emulating a physical pen in a computer system is to couple an input device with a computer display, and to integrate the writing behavior of the input device with the display, so that the surface which the user appears to be drawing upon is itself dynamically responsive to drawing strokes made by the user. See, e.g., U.S. Pat. No. 4,639,720 to Rympalski. While this method achieves the advantages of providing feedback to the user for written strokes, and of allowing the user to place the input device in a relatively exact relationship with written strokes which have already been drawn, it suffers from the drawbacks that such displays are relatively expensive and that such displays require relatively sophisticated transparent input device technology. For example, an input drawing tablet integrated with a video display can cost half as much as the computer to which it is connected. These limitations tend to restrict use of this technology to a very limited group.
A second known method for emulating a physical pen in a computer system is to provide an input tablet and stylus, in which the input tablet is capable of detecting proximity of the stylus and transmitting information regarding written strokes to a computer system for display on a monitor. An example of such a device is the Art Pad II product, available from Wacom Technology Corporation of Vancouver, Wash. While this method is relatively less expensive, it is also less successful at providing feedback to the user for written strokes, and in allowing the user to place the input device in a relatively exact relationship with written strokes which have already been drawn, because the user must draw or write with the input device on the tablet, while looking elsewhere (at the monitor) for feedback. This method also suffers from the drawback that the stylus requires electronic circuitry to assist proximity detection by the tablet. If the input device is tethered to provide an electrical connection, its ease of use and naturalness can be significantly degraded, while if the input device is not tethered, it can easily be lost, which can be quite expensive.
A third method for emulating a physical pen in a computer system is to provide a stylus having a switch which activates when a selected pressure threshold is exceeded, and which is coupled to the computer system for processing. Thus, when the user exerts relatively heavy pressure, the computer system will treat the stylus as a drawing device for creating written strokes, while when the user exerts only relatively light pressure, the computer system will merely reposition its reference point for the stylus (represented by a cursor) and allow the user to begin a written stroke from a new position.
While this method achieves the advantages of providing feedback to the user for written strokes, and in allowing the user to place the input device in a relatively exact relationship with written strokes which have already been drawn, it suffers from the drawback that it is very difficult for the user to control the exact amount of pressure being exerted, and thus causes inadvertent switching between a drawing mode and a repositioning mode, which may thus result in user dissatisfaction.
Accordingly, it would be desirable to provide a method and system for drawing or writing using a stylus as an input device in computer systems.
It is therefore an object of the present invention to provide an inexpensive input device for creating drawings on computers.
It is a further object of the present invention to provide an inexpensive input device for creating drawings on computers which eliminates the accidental switching between cursor mode and inking mode.
Yet another object of the present invention is to provide a system and method for allowing drawings to be made with relatively small tablets.
The advantages of the present invention are achieved in an embodiment of the invention in which switching between a drawing mode and a repositioning mode is convenient and natural, while using only a relatively inexpensive passive stylus and even while using a tablet or touchpad having a substantially smaller size than the computer system display.
The invention provides a method and system for drawing or writing using a passive stylus input device in computer systems. The system provides an absolute-coordinate drawing mode, in which the user may draw written strokes to which the computer system display is responsive, and a relative-coordinate repositioning mode (herein sometimes called a xe2x80x9ccursorxe2x80x9d mode), in which the user may figuratively xe2x80x9cpick up the penxe2x80x9d and reposition the beginning of a following written stroke. The system enters the drawing mode in response to a user command (such as a drawing gesture, tap performed on the input tablet, or selected keyboard command), and remains in the drawing mode in response to continued written strokes. The system enters the cursor mode after a selected time period occurs with no written strokes, or in response to other system events (such as keyboard input).
In the drawing mode, a coordinate system for the touchpad is mapped to a coordinate system for a selected window on the display. The mapping is selected so that an initial position of a written stroke in the window corresponds to a final position selected during the previous cursor mode, so that the user is able to reposition the input device in the case when it has (or was about to) xe2x80x9crun off the edgexe2x80x9d of an input tablet which is relatively smaller than the display.
In a presently preferred embodiment, the system uses either a resistive touchpad input tablet, or a capacitive touchpad input tablet in conjunction with a stylus having a flexible conductive writing tip.
In alternative embodiments, the system provides a signature mode, in which the user is able to make a simple drawing, such as a handwritten signature.